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failed system reachability
status checks


My instance is failing one or both of its status checks, and is unreachable. What does this mean, and how do I resolve this issue? 

Amazon Elastic Compute Cloud (EC2) verifies the health and reachability of an instance by means of frequent status checks on every running EC2 instance. Status checks serve as the first indicators of the plausible root cause of an instance being unreachable. There are two types of status checks:

  • System status check: The system status check detects issues with the underlying host that your instance runs on. If the underlying host is unresponsive or unreachable due to network, hardware, or software issues, then this status check fails.
  • Instance status check: This status check is concerned with the response and low-level reachability of the instance itself and the guest OS. The instance status check monitors an instance's response by making low-level Address Resolution Protocol (ARP) requests to the virtualized elastic network interface.

For more information, see Types of Status Checks.

When an instance is unreachable and has failed the system status check

When there is a problem with an underlying host, the best way to resolve the issue is to migrate from the underlying host by stopping and starting your instance.

In rare circumstances, the infrastructure-layer issue can prevent the underlying host from responding to the stop-start call. This causes the instance to be stuck in the stopping state.

You can create an Amazon CloudWatch alarm that monitors and automatically recovers the EC2 instance from any issue that requires AWS involvement.

When an instance is unreachable and has failed the instance status check

The instance status check can fail due to any number of reasons, such as failure to boot the operating system, failure to mount volumes correctly, file system issues, incompatible drivers, kernel panic, severe memory pressures, and so on. These failures can be anything that prevents the virtualized elastic network interface from coming up and being responsive.

Because instance status checks are likely caused by issues within the guest operating system, troubleshooting such issues should focus on reviewing console output, system logs, and the nature of the error messages:

You can easily diagnose and automate remediation processes using EC2Rescue:

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Published: 2014-07-03

Updated: 2019-03-20